CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

2D airfoil simulation, turbulence, boundary layer, unstructured grid

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   March 3, 2010, 09:19
Default 2D airfoil simulation, turbulence, boundary layer, unstructured grid
  #1
New Member
 
Louis LANGOUCHE
Join Date: Feb 2010
Posts: 1
Rep Power: 0
louis.langouche@gmail.com is on a distinguished road
Dear all,

I'm doing flow simulations on an airfoil in order to resolve the aerodynamic loads on this airfoil. I use an unstructured grid since geometries might change a lot for following planned simulations. The airfoil has 1m chord, 68m/s airspeed (mach 0.2), Re=4.5*10^6, Turbulence intensity 0.5%, Turbulence Length Scale 0.0075m

As you can see on this graph, there is a big discrepancy between the simulated lift coefficient and the reference data.



I worked with 2 different grids, the first with unstructured boundary layer, resulting in a scattered Y+ chart. The second with a more stable Y+ chart, nevertheless showing the same trends:



As you can see, the Y+ values jump under 30 and over 300 over a short range.

The methods result in bad Cp distributions:


After integration, the lift coefficients are bad.

I'm dealing with a list of questions:
1. What is the effect of 'some points' out of Y+ range 30-300?
2. How can I keep the Y+ chart more stable? Since I need to check grid independency, I will have to refine. Refinement now will result in Y+ values further below 30.
3. Is an unstructured boundary layer problematic, or is it feasible?
4. Are the inlet turbulence entities reasonable.
5. Is the domain big enough?
6. My integration method to resolve the loads, is done based purely on pressure distribution. Mustn't speed be included since viscosity will affect drag coefficient?

A view of the pathlines:


Most sincerely,

Louis (Belgium)
louis.langouche@gmail.com is offline   Reply With Quote

Reply

Tags
airfoil, boundary, spalart allmaras, turbulence, unstructured

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
To thin boundary layer? Luk CFX 3 February 27, 2009 04:22
Airfoil boundary condition Frank Main CFD Forum 1 April 21, 2008 18:36
Boundary layer simulation - convergence problems Gavin Tabor Main CFD Forum 3 July 2, 2004 05:16
errors Fahad Main CFD Forum 0 March 23, 2004 14:20
Combustion Convergence problems Art Stretton Phoenics 5 April 2, 2002 05:59


All times are GMT -4. The time now is 17:51.